This invention relates to a ball-holder of a ball-point pen, in which a writing ball is rotatably supported in a metallic tube and a rod is inserted in the tube to guide the ink, and more particularly to a ball-holder in which the ink guide rod is fixed in the tube without preventing the ink from flowing smoothly in the ball-holder.
In the case of a ball-point pen, a ball-holder having a writing ball and an ink guide rod of plastics for supplying the ink from an ink reservoir to the ball, is known, for example, as disclosed in U.S. Pat. No. 3,904,297. The writing ball is held in a reduced diameter portion of the metallic tube located at one end of the tube and formed by press-deforming of the tube so that a part of the ball projects from the reduced diameter portion. The rod is loosely inserted into the tube in such a manner that one end face of the same is used as a ball seat. The ink is delivered to the ball through a gap or clearance between the outer circumference of the rod and the inner circumference of the tube from an ink reservoir. Therefore the rod needs to be fixed fast in the tube so that the ball is not pushed back by the writing pressure.
For the purpose of fixing the rod in the tube, there has been employed a method in which the other end of the tube is formed with a constriction, or the other end of the rod is dimensioned to abut against a part of the body of the ball-pint pen itself. However, when the thin rod is fixed in the tube by being fixed at the portion opposite the ball seat-forming end, the state in which the ball and the ball seat-forming end contact with each other changes, because the coefficients of linear expansion of the metallic tube and the synthetic resin-made rod are different from each other. As a result, the writing efficiency may be lowered.
In order to overcome this disadvantage, and as described in Japanese utility model Application Laid Open No. 55-148984, there has been proposed a ball-holder in which the rod is held in the tube by being fixed at a portion close to the ball seat-forming end of the rod. This ball-holder is advantageous in that, because of the fixing point being close to the ball seat-forming end, the contacting state between the ball and the ball seat-forming end will change slightly even though the coefficients of linear expansion of the metallic tube and the rod are different from each other. To fix the rod in the metallic tube in this construction, three or more suitably spaced projections projecting toward the axis of the tube are made circumferentially of the tube thereby press-deforming the tube. If the metallic tube and the rod are fixed strongly enough, in this way, the ink channel between the tube and the rod is disrupted by the projections and the flow of the ink may be disturbed.